Key Laboratory of Mariculture, Ministry of Education (KLMME), Ocean University of China, Qingdao 266003, China.
Int J Mol Sci. 2022 Aug 4;23(15):8691. doi: 10.3390/ijms23158691.
Smolting is an important development stage of salmonid, and an energy trade-off occurs between osmotic regulation and growth during smolting in rainbow trout (Oncorhynchus mykiss). Growth hormone releasing hormone, somatostatin, growth hormone and insulin-like growth factor (GHRH-SST-GH-IGF) axis exhibit pleiotropic effects in regulating growth and osmotic adaptation. Due to salmonid specific genome duplication, increased paralogs are identified in the ghrh-sst-gh-igf axis, however, their physiology in modulating osmoregulation has yet to be investigated. In this study, seven sst genes (sst1a, sst1b, sst2, sst3a, sst3b, sst5, sst6) were identified in trout. We further investigated the ghrh-sst-gh-igf axis of diploid and triploid trout in response to seawater challenge. Kidney sst (sst1b, sst2, sst5) and sstr (sstr1b1, sstr5a, sstr5b) expressions were changed (more than 2-fold increase (except for sstr5a with 1.99-fold increase) or less than 0.5-fold decrease) due to osmoregulation, suggesting a pleiotropic physiology of SSTs in modulating growth and smoltification. Triploid trout showed significantly down-regulated brain sstr1b1 and igfbp2a1 (p < 0.05), while diploid trout showed up-regulated brain igfbp1a1 (2.61-fold, p = 0.057) and igfbp2a subtypes (1.38-fold, p < 0.05), suggesting triploid trout exhibited a better acclimation to the seawater environment. The triploid trout showed up-regulated kidney igfbp5a subtypes (6.62 and 7.25-fold, p = 0.099 and 0.078) and significantly down-regulated igfbp5b2 (0.37-fold, p < 0.05), showing a conserved physiology of teleost IGFBP5a in regulating osmoregulation. The IGFBP6 subtypes are involved in energy and nutritional regulation. Distinctive igfbp6 subtypes patterns (p < 0.05) potentially indicated trout triggered energy redistribution in brain and kidney during osmoregulatory regulation. In conclusion, we showed that the GHRH-SST-GH-IGF axis exhibited pleiotropic effects in regulating growth and osmoregulatory regulation during trout smolting, which might provide new insights into seawater aquaculture of salmonid species.
驯化是鲑鱼目的一个重要发育阶段，在虹鳟（Oncorhynchus mykiss）驯化过程中，渗透调节和生长之间会发生能量权衡。生长激素释放激素、生长抑素、生长激素和胰岛素样生长因子（GHRH-SST-GH-IGF）轴在调节生长和渗透适应方面表现出多效性。由于鲑鱼科的特异性基因组重复，在 ghrh-sst-gh-igf 轴中鉴定出了增加的基因，然而，它们在调节渗透压中的生理学功能尚未得到研究。在这项研究中，在鳟鱼中鉴定出了 7 个 sst 基因（sst1a、sst1b、sst2、sst3a、sst3b、sst5、sst6）。我们进一步研究了二倍体和三倍体鳟鱼在海水挑战下的 ghrh-sst-gh-igf 轴。肾脏 sst（sst1b、sst2、sst5）和 sstr（sstr1b1、sstr5a、sstr5b）的表达发生了变化（增加了 2 倍以上（除 sstr5a 增加了 1.99 倍）或减少了不到 0.5 倍），这表明 SSTs 在调节生长和驯化方面具有多效生理学功能。三倍体鳟鱼表现出大脑 sstr1b1 和 igfbp2a1 的显著下调（p < 0.05），而二倍体鳟鱼表现出大脑 igfbp1a1 的上调（约 2.61 倍，p = 0.057）和 igfbp2a 亚型的上调（约 1.38 倍，p < 0.05），表明三倍体鳟鱼对海水环境的适应能力更强。三倍体鳟鱼的肾脏 igfbp5a 亚型上调（约 6.62 和 7.25 倍，p = 0.099 和 0.078）和 igfbp5b2 显著下调（约 0.37 倍，p < 0.05），表明硬骨鱼 IGFBP5a 在调节渗透压方面具有保守的生理学功能。IGFBP6 亚型参与能量和营养调节。独特的 igfbp6 亚型模式（p < 0.05）可能表明鳟鱼在渗透压调节过程中在大脑和肾脏中触发了能量再分配。总之，我们表明，GHRH-SST-GH-IGF 轴在调节鲑鱼驯化过程中的生长和渗透压调节方面表现出多效性，这可能为鲑鱼科海水养殖提供新的见解。
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